Today is the 2018 London Marathon and the sun is out, whether the competitors like it or not.
The question is, will it be the hottest marathon race on record considering the mini-heatwave we have been experiencing?
The race is 26.2 miles, which will be a huge test of stamina for even the most seasoned runners, and sunshine is another obstacle to face.
The mercury is apparently going to hit 23C in the city today, with a Met Office spokesperson saying there will be pleasant, warm conditions.
This actually means theres a good chance it could be the hottest London Marathon on record.
The hottest London marathon on record was 22.7C in 1996. This year might see that record smashed, and it will very likely beat the 21.5C record from 2007.
Organisers are adding more water, ice and shower stations along the route, which begins in Greenwich Park and ends by St James Park.
Mascot-style runners are being encouraged not to wear costumes.
Even regular runners are being advised to consider dropping their goal-times and run more slowly.
Despite these warnings, the Grenfell firefighters have said they will still run the course in their full uniform.
Back in 2007, run-through showers were installed along the track and increased the bottled water stock from 25,000 to over 27,000.